Electron multiplier



Jan. 2, 1940.

E. STEUDEL ET AL 2,185,611

ELECTRON MULTIPLIEHR Filed Feb. 15. 19:57

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INVENTORS EBERHARD STEUDEL RICHARD ORTHUBER ATTO RN EY Patented Jan. 2 1940 1 UNITED STATES:

ELECTRON MULTIPLIER" Eberhard Steudel, Berlin-Dahlem, and Richard Orthuber, Berlin, Germany, assignors to Allgemeine Elektricitats-Gesellschaft, Berlin, Ger

many

Application February 15, 1937, Serial No. 125,824

In Germany February 26, 1936 3 Claims.

There are known secondary electron multipliers, especially for the amplification of photocurrents, in the form of photo-tubes in which, besides a photo-cathode, also one or several secondary cathodes are provided which are intended to emit secondary electrons. The output of such a photo-tube depends upon the original output of the photo-cathode as regards primary electrons, as well as on theprobability asto whether or not the secondary cathodes are hit by the dispersed electronor light-rays.

The present invention relates to an arrangement in which said output is particularly great. According to this invention, the cathode consists of a tuft of threads which all at the same time serve for the primary and the secondary emission of electrons.

The invention is illustrated diagrammatically .and by way of example on the accompanying drawing on which is shown an arrangement and combination of parts designed according to this invention. Figure 1 shows the entire arrangement, Figure 2 certain details thereof drawn to anenlarged scale relatively to Fig. 1.

The numeral I (Fig. 1) denotes the rays of light which fall on a tuft of threads 2 consisting, for instance, ofglass and being covered with a substance, for instance caesium, able to emitamply a light-electric and a secondary emission; these threads are supported on a member 3. Thethreads 2 and said member 3 constitute together a cathode which is surrounded rotationally-symmetrically' with a cylindrical anode 4. Between the cathode 2, -3 and the anode 4 lies a source of potential 5 which delivers the current that is to be measured with the a measuring instrument 6.

In order to enable the primary electrons reaid of leased in the cathode to release secondary electrons certain portions of the cathode must lie on a more positivematerial than other portions. Therefore, several cathode leads I, 8, 9 (Fig. 2) are provided, of which the most negative one (1) leads to the middle portion of the cathode, the most positive one (9) leads, however, to the rim of the same; The supporting member 3 consists of an insulating substance into which are embedded several conducting rings or the like I0, each of which contains a tuft of threads. The conducting tuft-bearing members [0 are connected with the leads 1, 8 and 9, so that,

therefore, the middle tuft is that which is most negative and the light-electric electrons released in it are able to release secondary electrons at the outer tufts, Just so, the light-electric or secondary electrons released in the tuft with the lead 8 are able to release secondary electrons also at the most outwardly located tufts.

(Cl. 250174)- A firstly, the entire surface of the cathode is very large and delivers, therefore, a considerable amount of 'primary electron emission, secondly, the entire large cathode surface is utilised at the same time for the secondary emission, and thirdly, owing to the electric field being directed perpendicularly to the tufts and radially, a very great probability is established that the tufts are hit by electrons emitting secondary electrons.

The secondary electron multiplier designed according to this invention is suited not only for use as a photo-tube, but can be employed also as multiplier for another radiation, for instance for cathode rays, if a suitable aperture for the entrance of these rays, for instance a Lenard window, is provided.

We claim:

anode member, a composite electrode'centrally positioned relative thereto comprising a plurality of separate tuftsof electron emissive thread-j nected thereto whereby they may be maintained 1. An electronic multiplier tube comprising an at different negative potentials'with respect to said anode member. I

2. An electron tube comprising a ring-like anode, a composite electrode centrally located relative thereto comprising a plurality of mutually insulated tufts of electron emissive threadlike members, and. leads connected thereto whereby said tufts are adapted tobe maintained at potentials increasing in a negative sense relative to the anode in accordance with theradial distance to each tuft from said anode in order'that each may emit primary and secondary electrons simultaneously.

3. An electronic multiplier device comprising a cylindrical anode membenan electrode mount positioned internally of the anode member and symmetrically located relative thereto, said mount comprising an insulated member and a plurality of individual tufts of electron emissive elements supported within the insul'atingmaterial, and conducting elements supported by the insulating material and individually connected" to the separate tufts of the electron emissive elements.

EBERHARD STEUDEL; RICHARD ORTI-IUBER, 

